By Dr. Vishal Wadhwa
Genomics is a study of genes and chromosomes which can be applied for disease diagnosis, and to improve human life through its various applications in preventive treatments. Therefore, it has a role to play in both in Wellness and Illness. As science progresses, Genomics would target wellness that sits on the other side of the coin, which is illness. When we talk about wellness what comes to our mind is a dynamic lifestyle, which encompasses various aspects including self-reliance, physical fitness, nutritional awareness, stress management, and environmental sensitivity; but we need to be aware that this branch of science can help people with high-risk towards certain genetic conditions to make the correct choice be it for treatment or for making their future-generation healthy. We exemplify this with a small discussion on Thalassemia.
Thalassemia is a genetic blood disorder where in patients suffer from reduction of haemoglobin in the body. Unlike other haemoglobinopathies where there is a structural & functional defect in haemoglobin, thalassemic patients have less or absent α or β haemoglobin chains which form haemoglobin. Depending upon haemoglobin chain affected thalassemia is classified into two common types β and α thalassemia. The prevalence of thalassemia trait in India is around 3-4%, but because of consanguinity, caste and area endogamy, some communities show a very high incidence, making the disease a public health problem. A retrospective data analysis done at Metropolis Healthcare Ltd with 106277 suspected cases of hemoglobinopathies, Beta thalassemia trait was found in 9817 cases (9.23%). This shows that thalassemia is not just in our textbooks but is being endured by many in our country.
Patients with β-thalassemia-major typically present in early childhood with severe anaemia, hepatosplenomegaly (enlarged liver and spleen), and failure to thrive; while thalassemia intermedia present later in life and have milder anaemia. Genetically, there are two HBB genes with allelic representations. Carriers of β-thalassemia have a single gene having β0/β+ mutation with the other gene being normal; on the extreme end are thalassemia major patients who have both genes affected. Genes responsible for formation of the alpha & beta chains of haemoglobin are situated on chromosome 16 and chromosome 11. As an example, will discuss the role of genomics in β- thalassemia.
While red cell indices and haemoglobin electrophoretic/ chromatographic studies help achieve clinical diagnosis, but conclusive proof is achieved through beta globin gene sequencing.
At Metropolis Healthcare Ltd, PCR-Sanger sequencing method is used to detect over common 30 mutations in the beta globin gene that can cause β- thalassemia and additionally detects four structurally abnormal variants of β-globin chain namely sickle cell anemia, Haemoglobin E, D and C.
Just like ‘stars’ are for astrology believers, genomic testing should be considered by those coming from at-risk thalassemia families. Beta globin (HBB) gene sequencing should be done for those seeking marriage in family and where history of thalassemia is present, so that they can take a voluntary decision. Wanna-be parents from ‘at risk’ population with thalassemia trait (carrier) have two options: First, at the time of pregnancy, the Beta globin gene sequencing from the chorionic villus biopsy or amniotic fluid analysis can detect mutation and future thalassemia phenotype and can help prepare parents for the future. Second, couple can also go for the pre-implantation genetic testing to select the embryo (PGTM – pre-implantation embryonic genetic testing) that does not have the thalassemia gene or any aneuploidy. Thus, it can ensure birth of a non-thalassemia major child despite parents being thalassemia carriers. But before one proceeds with any of such intervention, it is important that a genetic counsellor is consulted, and precision guidance is taken.
(The author is the Head of Scientific Affairs, Metropolis Healthcare Ltd.. Views expressed are personal and do not reflect the official position or policy of FinancialExpress.com.)
